A third effect, which we do not consider here, is agent heterogeneity. Most existing work assumes
that the members of the swarm are identical. However, many practical
applications involve swarms that are composed of agents with differing
dynamical properties from the onset, or that become different over time due to
malfunction or aging. Swarm heterogeneity leads to interesting new collective
dynamics such as spontaneous segregation of the various populations within the
swarm; it also has the potential to erode swarm cohesion. In biology, for
example, it has been shown that sorting behavior of different cell types
during the development of an organism can be achieved simply by introducing
heterogeneity in inter-cell adhesion properties
[1]}, [2]}. In robotic systems, allowing for
heterogeneity in dynamical behaviors of swarm agents gives greater flexibility
in system design, and is therefore desirable not only from a theoretical but
also from a practical point of view [3]}.
